Gowtham Radhakrishnan, Bernt J. Leira, Zhen Gao, Svein Savik, Xu Han
Abstract From a mathematical viewpoint, the frequency domain analysis of vessel motion responses due to wave actions is based on integration of system dynamics idealized in terms of response amplitude operators (RAOs) for 6 DOF rigid body motions and an input wave spectrum in order to obtain the response spectrum. Various quantities of interest can be deduced from the response spectrum which are then used for deriving response-based operational limits for marine operations, also including extreme value and fatigue analysis. The variation of such quantities, owing to the uncertainties associated with the vessel system parameters, can be quantified by performing uncertainty propagation (UP) and consequent sensitivity analysis (SA). This study emphasizes and proposes a computational-efficient way of assessing the sensitivity of the system model output with respect to the uncertainties residing in the input parameters by operating on a surrogate model representation. In this respect, the global sensitivity analysis was effectively carried out by deploying an efficient non-intrusive polynomial chaos expansion (PCE) surrogate model built using a point collocation strategy. Successively, the Sobol' indices were obtained from the analytical decomposition of the polynomial coefficients. The indices, eventually, are employed to quantitatively measure the effects of input uncertainties on the output 6 DOF vessel Root Mean Square responses.
{"title":"Analyzing the sensitivity of wave frequency responses of floating vessels to uncertain system variables utilizing Polynomial Chaos Expansion","authors":"Gowtham Radhakrishnan, Bernt J. Leira, Zhen Gao, Svein Savik, Xu Han","doi":"10.1115/1.4063619","DOIUrl":"https://doi.org/10.1115/1.4063619","url":null,"abstract":"Abstract From a mathematical viewpoint, the frequency domain analysis of vessel motion responses due to wave actions is based on integration of system dynamics idealized in terms of response amplitude operators (RAOs) for 6 DOF rigid body motions and an input wave spectrum in order to obtain the response spectrum. Various quantities of interest can be deduced from the response spectrum which are then used for deriving response-based operational limits for marine operations, also including extreme value and fatigue analysis. The variation of such quantities, owing to the uncertainties associated with the vessel system parameters, can be quantified by performing uncertainty propagation (UP) and consequent sensitivity analysis (SA). This study emphasizes and proposes a computational-efficient way of assessing the sensitivity of the system model output with respect to the uncertainties residing in the input parameters by operating on a surrogate model representation. In this respect, the global sensitivity analysis was effectively carried out by deploying an efficient non-intrusive polynomial chaos expansion (PCE) surrogate model built using a point collocation strategy. Successively, the Sobol' indices were obtained from the analytical decomposition of the polynomial coefficients. The indices, eventually, are employed to quantitatively measure the effects of input uncertainties on the output 6 DOF vessel Root Mean Square responses.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135696526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Artificial reefs (ARs) are one of the key anthropogenic constructs used to restore offshore fishery resources and recover the ecological environment. However, many ARs lose their stability and function due to scour. To ensure the functional effect of ARs, it is of great significance to study the factors causing AR instability, such as burying caused by scour under different flow conditions. In present study, a three-dimensional numerical model is established in FLOW-3D to study the local scour characteristics around an AR in steady currents. Reynolds-averaged Navier–Stokes (RANS) equations, closed with the renormalization group (RNG) k–ɛ turbulence model, are established to simulate a stable flow field around one AR. The simulation results are compared with previous experimental results, exhibiting good agreement. The effects of the opening number and the incident angles of ARs on the scour characteristics, equilibrium scour depth, and maximum scour volume were also investigated. The results indicate that the scour depth and scour volume decreased as the opening number increased. Furthermore, empirical equations are proposed herein based on the numerical results derived for the effects of the AR opening number on the equilibrium scour depth and maximum scour volume. A change in the incident angle affected the bed shear stress at the most-upstream corner of the AR. The greater the bed shear stress was, the more intense the scour was. In this study, we provide theoretical support and practical guidance for the optimized engineering design and construction of ARs.
摘要人工鱼礁是近海渔业资源恢复和生态环境恢复的关键人工设施之一。然而，许多ar由于冲刷而失去了稳定性和功能。为了保证AR的功能效果，研究不同流动条件下冲刷引起的埋地等导致AR不稳定的因素具有重要意义。本文在FLOW-3D中建立了一个三维数值模型，研究了稳流条件下AR周围的局部冲刷特性。采用重整化群(RNG) k - ε湍流模型，建立了雷诺数平均Navier-Stokes (RANS)方程，模拟了一个AR周围的稳定流场，并将模拟结果与已有的实验结果进行了比较，结果吻合较好。研究了开口数和入射角对射流冲刷特性、平衡冲刷深度和最大冲刷体积的影响。结果表明:随着开孔数的增加，冲刷深度和冲刷体积减小;在此基础上，根据数值计算结果，提出了AR开孔数对平衡冲刷深度和最大冲刷体积影响的经验方程。入射角的变化会影响坝体最上游角的床层剪应力，床层剪应力越大，冲刷越剧烈。通过本研究，为ar优化工程设计和施工提供理论支持和实践指导。
{"title":"Numerical Simulation of Local Scour Around a Square Artificial Reef","authors":"Mingda Yang, Yanli Tang, Fenfang Zhao, Shiji Xu, Guangjie Fang","doi":"10.1115/1.4062591","DOIUrl":"https://doi.org/10.1115/1.4062591","url":null,"abstract":"Abstract Artificial reefs (ARs) are one of the key anthropogenic constructs used to restore offshore fishery resources and recover the ecological environment. However, many ARs lose their stability and function due to scour. To ensure the functional effect of ARs, it is of great significance to study the factors causing AR instability, such as burying caused by scour under different flow conditions. In present study, a three-dimensional numerical model is established in FLOW-3D to study the local scour characteristics around an AR in steady currents. Reynolds-averaged Navier–Stokes (RANS) equations, closed with the renormalization group (RNG) k–ɛ turbulence model, are established to simulate a stable flow field around one AR. The simulation results are compared with previous experimental results, exhibiting good agreement. The effects of the opening number and the incident angles of ARs on the scour characteristics, equilibrium scour depth, and maximum scour volume were also investigated. The results indicate that the scour depth and scour volume decreased as the opening number increased. Furthermore, empirical equations are proposed herein based on the numerical results derived for the effects of the AR opening number on the equilibrium scour depth and maximum scour volume. A change in the incident angle affected the bed shear stress at the most-upstream corner of the AR. The greater the bed shear stress was, the more intense the scour was. In this study, we provide theoretical support and practical guidance for the optimized engineering design and construction of ARs.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136010512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In this paper, to determine the efficacy of the porous bed on damping far-field wave energy the wave dynamics around a circular plate is studied. By combining the appropriate boundary conditions, the unknown potential is attained for the free surface and the plate-covered region. The Bessel series solution is attained further, by employing the matched eigenfunction expansion technique. Wave force excitation on the circular plate, deflection of the plate, and flow distribution is calculated and examined to comprehend the efficacy of the current investigation. Moreover, the motion of the plate is assessed in the time domain. The study reveals a substantial reduction in wave amplitude on the plate's leeward side because of the energy dissipation by the porous bed. Also the study concludes that for intermediate values of porosity with larger wavenumbers, approximately 50% of wave power is dissipated with respect to incident wave power.
{"title":"Wave dynamics around a floating circular flexible plate over a permeable bed","authors":"Gayathri R., Chia-Cheng Tsai, Harekrushna Behera","doi":"10.1115/1.4063492","DOIUrl":"https://doi.org/10.1115/1.4063492","url":null,"abstract":"Abstract In this paper, to determine the efficacy of the porous bed on damping far-field wave energy the wave dynamics around a circular plate is studied. By combining the appropriate boundary conditions, the unknown potential is attained for the free surface and the plate-covered region. The Bessel series solution is attained further, by employing the matched eigenfunction expansion technique. Wave force excitation on the circular plate, deflection of the plate, and flow distribution is calculated and examined to comprehend the efficacy of the current investigation. Moreover, the motion of the plate is assessed in the time domain. The study reveals a substantial reduction in wave amplitude on the plate's leeward side because of the energy dissipation by the porous bed. Also the study concludes that for intermediate values of porosity with larger wavenumbers, approximately 50% of wave power is dissipated with respect to incident wave power.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136060564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As the latest development of gravity installed anchors (GIAs), the OMNI-Max anchor has drawn much attention from worldwide due to its unique behavior in the seabed. The pullout capacity of OMNI-Max anchors is a key index in engineering. However, most of the relevant studies were carried out under a quasi-static condition, which do not actually meet the installation and operation requirements. In practice, the anchor may be subjected to both long-term and short-term sharp loading during mooring. As an important environmental variable, it is essential to evaluate the effect of loading rate on the pullout capacity. Since the bearing capacity of OMNI-Max anchors is affected by many factors, it is also essential to explore systematically the coupling effects of the loading rate and other factors, including the anchor embedment depth, the anchor orientation, the bearing area, the loading angle and the soil strength. Based on the coupled Eulerian-Lagrangian (CEL) technique, numerous analytical cases are designed and calculated by the large deformation finite element (LDFE) method. The loading rates span four orders of magnitude from the quasi-static velocity to 10 m/s (about one anchor length per second), covering a wider range in pulling out of GIAs. The end-bearing capacity factor changes remarkably with the pullout velocity for OMNI-Max anchors, and the increase can even reach more than twice of that in a quasi-static condition. As a result, a succinct explicit expression is constructed in terms of the loading rate and multiple factors, which can be effectively utilized to calculate the end-bearing capacity factor of OMNI-Max anchors in clay under complex conditions.
{"title":"Loading rate effect on the pullout capacity of OMNI-Max anchors in clay coupled with multiple factors","authors":"Haixiao Liu, Yancheng Yang, Heng Xu","doi":"10.1115/1.4063332","DOIUrl":"https://doi.org/10.1115/1.4063332","url":null,"abstract":"\u0000 As the latest development of gravity installed anchors (GIAs), the OMNI-Max anchor has drawn much attention from worldwide due to its unique behavior in the seabed. The pullout capacity of OMNI-Max anchors is a key index in engineering. However, most of the relevant studies were carried out under a quasi-static condition, which do not actually meet the installation and operation requirements. In practice, the anchor may be subjected to both long-term and short-term sharp loading during mooring. As an important environmental variable, it is essential to evaluate the effect of loading rate on the pullout capacity. Since the bearing capacity of OMNI-Max anchors is affected by many factors, it is also essential to explore systematically the coupling effects of the loading rate and other factors, including the anchor embedment depth, the anchor orientation, the bearing area, the loading angle and the soil strength. Based on the coupled Eulerian-Lagrangian (CEL) technique, numerous analytical cases are designed and calculated by the large deformation finite element (LDFE) method. The loading rates span four orders of magnitude from the quasi-static velocity to 10 m/s (about one anchor length per second), covering a wider range in pulling out of GIAs. The end-bearing capacity factor changes remarkably with the pullout velocity for OMNI-Max anchors, and the increase can even reach more than twice of that in a quasi-static condition. As a result, a succinct explicit expression is constructed in terms of the loading rate and multiple factors, which can be effectively utilized to calculate the end-bearing capacity factor of OMNI-Max anchors in clay under complex conditions.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48091224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sihan Gao, F. Oppedal, Jan Olav Fosse, S. Tuene, L. Gansel
This paper presents field tests on a full-scale cage, with and without fish, being pushed by a boat in Masfjorden at various speeds. The purpose was to imitate the exposure of net cages to different currents. The tests involved measuring cage deformations, fish behaviors, and the corresponding flow upstream, downstream, and inside the cage. The study found that the experimental setup used can achieve predictable and stable upstream flow for a full-scale net cage. Based on pressure tag data, the volume reductions of the cage, both with and without fish, were estimated at different speeds. Both cases show a similar trend of cage volume reduction with respect to flow speeds as the previous studies. Moreover, the presence of fish had limited influence on the net volume change. The reduction in speed inside and downstream from the cage was within the range reported in previous literature. Notably, when the cage becomes significantly deformed, it not only reduces flow speed but also alters flow directions, as evidenced by the high variability of flow direction inside the empty cage, particularly at high speeds. The measured flow speed inside the stocked cage also exhibited high variability, but the pattern of variation differed significantly from that of the empty cage, indicating the influence of fish. These findings suggest that traditional flow speed models might oversimplify the flow field in and around fish cages, especially in studies concerning the dispersion of particles, pathogens, and dissolved matter in and out of fish cages.
{"title":"Fluid-structure interactions of net cages - full-scale pushing tests in the field","authors":"Sihan Gao, F. Oppedal, Jan Olav Fosse, S. Tuene, L. Gansel","doi":"10.1115/1.4063264","DOIUrl":"https://doi.org/10.1115/1.4063264","url":null,"abstract":"This paper presents field tests on a full-scale cage, with and without fish, being pushed by a boat in Masfjorden at various speeds. The purpose was to imitate the exposure of net cages to different currents. The tests involved measuring cage deformations, fish behaviors, and the corresponding flow upstream, downstream, and inside the cage. The study found that the experimental setup used can achieve predictable and stable upstream flow for a full-scale net cage. Based on pressure tag data, the volume reductions of the cage, both with and without fish, were estimated at different speeds. Both cases show a similar trend of cage volume reduction with respect to flow speeds as the previous studies. Moreover, the presence of fish had limited influence on the net volume change. The reduction in speed inside and downstream from the cage was within the range reported in previous literature. Notably, when the cage becomes significantly deformed, it not only reduces flow speed but also alters flow directions, as evidenced by the high variability of flow direction inside the empty cage, particularly at high speeds. The measured flow speed inside the stocked cage also exhibited high variability, but the pattern of variation differed significantly from that of the empty cage, indicating the influence of fish. These findings suggest that traditional flow speed models might oversimplify the flow field in and around fish cages, especially in studies concerning the dispersion of particles, pathogens, and dissolved matter in and out of fish cages.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43942496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wave runup prediction is necessary for the offshore structure designs and early warnings. Data-driven methods based on machine learning have inspired reduced-order solutions for wave-structure interaction problems. This study provides the quantification of deep learning algorithms' potential for wave runup prediction. Two prominent deep learning models were utilized to predict the wave runups along the fore column of semi-submersible under head seas. The long short-term memory (LSTM) and the temporal convolutional networks (TCN) were comprehensively compared based on the datasets from a model test carried out in the deep ocean basin. The LSTM and TCN model structures were optimized to compare prediction accuracy and computational complexity reasonably. The results reveal that: (1) both developed TCN and LSTM models had satisfied prediction accuracy of over 90 %. Their predictions were extended to 10 seconds into the future with accuracies over 80 % and 45 %, respectively. (2) With the noise-extended datasets, the LSTM model was robust to noises, while the TCN model showed better prediction performance on the extreme wave runup events. (3) The incident wave and dominant rotation provided the major information for wave runup prediction. TCN and LSTM models' prediction accuracies were 91.5 % and 89.3 % based on the simplified input tensors composed of incident wave and pitch. The comparison showed the great potential of TCN model to predict the nonlinear wave runup with less time and memory costs. The input tensors design and optimization based on physical understanding also play a significant role in the prediction performance.
{"title":"A Comparative Study of LSTM and TCN Models for Semi-submersible Platform Wave Runup Prediction","authors":"Yan Li, Longfei Xiao, Handi Wei, De-xin Li, Xu Li","doi":"10.1115/1.4063266","DOIUrl":"https://doi.org/10.1115/1.4063266","url":null,"abstract":"\u0000 Wave runup prediction is necessary for the offshore structure designs and early warnings. Data-driven methods based on machine learning have inspired reduced-order solutions for wave-structure interaction problems. This study provides the quantification of deep learning algorithms' potential for wave runup prediction. Two prominent deep learning models were utilized to predict the wave runups along the fore column of semi-submersible under head seas. The long short-term memory (LSTM) and the temporal convolutional networks (TCN) were comprehensively compared based on the datasets from a model test carried out in the deep ocean basin. The LSTM and TCN model structures were optimized to compare prediction accuracy and computational complexity reasonably. The results reveal that: (1) both developed TCN and LSTM models had satisfied prediction accuracy of over 90 %. Their predictions were extended to 10 seconds into the future with accuracies over 80 % and 45 %, respectively. (2) With the noise-extended datasets, the LSTM model was robust to noises, while the TCN model showed better prediction performance on the extreme wave runup events. (3) The incident wave and dominant rotation provided the major information for wave runup prediction. TCN and LSTM models' prediction accuracies were 91.5 % and 89.3 % based on the simplified input tensors composed of incident wave and pitch. The comparison showed the great potential of TCN model to predict the nonlinear wave runup with less time and memory costs. The input tensors design and optimization based on physical understanding also play a significant role in the prediction performance.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42712579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yongbo Chen, M. Hayatdavoodi, Binbin Zhao, R. Ertekin
We consider a horizontal, submerged plate in shallow water that is allowed to oscillate in the vertical direction due to the wave loads. The plate is attached to a linear spring and damper to control the oscillations. The focus of the study is on the transformation of the wave field by the submerged oscillating plate. To estimate energy scattering, wave reflection and transmission coefficients are determined from four wave gauges; two placed upwave and two placed downwave of the oscillating plate. The flow is governed by the nonlinear Level I Green-Naghdi (GN) equations, coupled with the equations of the vertical oscillations of the plate. Time series of water surface elevation recorded at gauges upwave and downwave of the plate obtained by the GN model are compared with the available laboratory experiments and other data, and very good agreement is observed. Wave reflection and transmission coefficients are then determined for a range of involved parameters, including wave conditions (wavelength and wave height), initial submergence depth of the plate, plate length, and the spring-damper system attached to the plate. It is found that a submerged oscillating plate can have a remarkable effect on the wave field, and that nonlinearity plays an important role in this wave-structure interaction problem. Discussion is provided on how the wave reflection and transmission coefficients vary with the wave conditions, plate characteristics, initial submergence depth and spring-damper system properties.
{"title":"Scattering of long waves by freely oscillating submerged plates","authors":"Yongbo Chen, M. Hayatdavoodi, Binbin Zhao, R. Ertekin","doi":"10.1115/1.4063181","DOIUrl":"https://doi.org/10.1115/1.4063181","url":null,"abstract":"\u0000 We consider a horizontal, submerged plate in shallow water that is allowed to oscillate in the vertical direction due to the wave loads. The plate is attached to a linear spring and damper to control the oscillations. The focus of the study is on the transformation of the wave field by the submerged oscillating plate. To estimate energy scattering, wave reflection and transmission coefficients are determined from four wave gauges; two placed upwave and two placed downwave of the oscillating plate. The flow is governed by the nonlinear Level I Green-Naghdi (GN) equations, coupled with the equations of the vertical oscillations of the plate. Time series of water surface elevation recorded at gauges upwave and downwave of the plate obtained by the GN model are compared with the available laboratory experiments and other data, and very good agreement is observed. Wave reflection and transmission coefficients are then determined for a range of involved parameters, including wave conditions (wavelength and wave height), initial submergence depth of the plate, plate length, and the spring-damper system attached to the plate. It is found that a submerged oscillating plate can have a remarkable effect on the wave field, and that nonlinearity plays an important role in this wave-structure interaction problem. Discussion is provided on how the wave reflection and transmission coefficients vary with the wave conditions, plate characteristics, initial submergence depth and spring-damper system properties.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46447495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Wisudawan, V. Jaksic, V. Pakrashi, Jimmy Murphy
Froude scaling for Floating Offshore Wind Turbine (FOWT) platforms is typical for understanding and interpreting their behavior and subsequent designs for testing in wave basins. Despite its popularity, the variability and uncertainty of the kinetic responses of such floating structures as a function of scaling require more attention. This work addresses the question of consistency of Froude scaling by comparing the hydrodynamic responses of a range of DeepCwind semi-submersible FOWT scaled models (full model, ½, ¼, 1/9, 1/16, 1/25, 1/36, 1/49 and 1/50). The comparation was made both in the mooring line tension and bending moment of structural members, which are directly related to their safety limit states. Hydrodynamic forces due to diffraction, radiation and viscosity along with hydrostatic forces and mooring boundaries are modeled by Ansys Aqwa, which were subsequently converted to bending moment estimates. The variability of kinetic responses like mooring line tensions and bending moment estimates was investigated for each scaled model, along with identification of regions of inconsistencies. In the context of offshore renewable energy development through technological readiness levels, the study is especially pertinent for understanding how force variabilities and uncertainties are related to these kinetic responses of semisubmersible platforms.
{"title":"Variability of Kinetic Response Estimates of Froude Scaled DeepCwind Semisubmersible Platforms Subjected to Wave Loading","authors":"A. Wisudawan, V. Jaksic, V. Pakrashi, Jimmy Murphy","doi":"10.1115/1.4063180","DOIUrl":"https://doi.org/10.1115/1.4063180","url":null,"abstract":"\u0000 Froude scaling for Floating Offshore Wind Turbine (FOWT) platforms is typical for understanding and interpreting their behavior and subsequent designs for testing in wave basins. Despite its popularity, the variability and uncertainty of the kinetic responses of such floating structures as a function of scaling require more attention. This work addresses the question of consistency of Froude scaling by comparing the hydrodynamic responses of a range of DeepCwind semi-submersible FOWT scaled models (full model, ½, ¼, 1/9, 1/16, 1/25, 1/36, 1/49 and 1/50). The comparation was made both in the mooring line tension and bending moment of structural members, which are directly related to their safety limit states. Hydrodynamic forces due to diffraction, radiation and viscosity along with hydrostatic forces and mooring boundaries are modeled by Ansys Aqwa, which were subsequently converted to bending moment estimates. The variability of kinetic responses like mooring line tensions and bending moment estimates was investigated for each scaled model, along with identification of regions of inconsistencies. In the context of offshore renewable energy development through technological readiness levels, the study is especially pertinent for understanding how force variabilities and uncertainties are related to these kinetic responses of semisubmersible platforms.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42821266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work investigates the hydrodynamic performance of a subsea shuttle, an extra-large freight submarine, during near-seabed operation. The three-dimensional Reynolds-Averaged Navier-Stokes method combined with the k-υ shear stress transport (SST) model is used to predict the pressure, skin friction, drag, and lift forces acting on the subsea shuttle. The present numerical model is verified and validated against the experimental and numerical data from the SUBOFF-1 project, a standard submarine model developed by the Defence Advanced Research Projects Agency. Two operational scenarios are considered in this study: (1) the subsea shuttle traveling near the seabed with a forward speed; (2) the subsea shuttle hovering close to the seabed and subject to an incoming current flow. A representative seabed boundary layer profile is considered in the analyses. A fully developed boundary layer profile is generated using one-dimensional simulations and implemented as the inlet boundary condition in the 3D simulations. The effects of the gap ratio between the subsea shuttle and the seabed, and the inflow speed of the boundary layer flow on the hydrodynamic properties of the subsea shuttle are evaluated and discussed in detail.
这项工作研究了海底穿梭船(一种超大型货运潜艇)在近海床作业期间的水动力性能。三维reynolds - average Navier-Stokes方法结合k-υ剪切应力传输(SST)模型，用于预测作用在水下穿梭器上的压力、表面摩擦、阻力和升力。目前的数值模型是根据来自SUBOFF-1项目的实验和数值数据进行验证和验证的，该项目是由国防高级研究计划局开发的一个标准潜艇模型。本研究考虑了两种操作场景:(1)水下穿梭船以正向速度靠近海床;(2)靠近海床悬停并受入流影响的水下穿梭器。分析中考虑了具有代表性的海底边界层剖面。利用一维模拟生成了一个完整的边界层轮廓，并在三维模拟中实现了入口边界条件。详细评价和讨论了海底穿梭器与海床间隙比、边界层水流入流速度对海底穿梭器水动力性能的影响。
{"title":"Numerical Investigation on Near-bottom Operation of an Extra-large Freight Submarine","authors":"Yucong Ma, G. Yin, M. Janocha, Y. Xing, M. Ong","doi":"10.1115/1.4063022","DOIUrl":"https://doi.org/10.1115/1.4063022","url":null,"abstract":"\u0000 This work investigates the hydrodynamic performance of a subsea shuttle, an extra-large freight submarine, during near-seabed operation. The three-dimensional Reynolds-Averaged Navier-Stokes method combined with the k-υ shear stress transport (SST) model is used to predict the pressure, skin friction, drag, and lift forces acting on the subsea shuttle. The present numerical model is verified and validated against the experimental and numerical data from the SUBOFF-1 project, a standard submarine model developed by the Defence Advanced Research Projects Agency. Two operational scenarios are considered in this study: (1) the subsea shuttle traveling near the seabed with a forward speed; (2) the subsea shuttle hovering close to the seabed and subject to an incoming current flow. A representative seabed boundary layer profile is considered in the analyses. A fully developed boundary layer profile is generated using one-dimensional simulations and implemented as the inlet boundary condition in the 3D simulations. The effects of the gap ratio between the subsea shuttle and the seabed, and the inflow speed of the boundary layer flow on the hydrodynamic properties of the subsea shuttle are evaluated and discussed in detail.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44238573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a fully coupled solution in the time-domain, using the finite-differences method to the system of equations that model the dynamic behavior of the riser, blow out preventer and casing strings, when connected for well drilling/completion – the model is suitable to evaluate wellhead fatigue, even when the amplitude of oscillation and accelerations of the BOP are high. Sensibility analysis is used to show the effect of changing the Riser Top Tension to the resulting maximum values of wellhead bending moment and casing stress ranges. For the case where the rig is oscillating around a fixed position and there is no current, using a regular wave, the results show that there are some wave periods for which an increase in the Riser Top Tension reduces the maximum wellhead bending moment and the max casing stress range, therefore increasing fatigue life of the casing and wellhead. The effects of varying the weight of the BOP and soil parameters and the effect of the phase difference between the wave and first order vessel motion are analyzed. The proposed solution can also be used to perform riser and casing analysis during drift-off/drive-off.
{"title":"DYNAMICS OF THE SYSTEM DRILLING RISER-BOP-WELL CASING – WELLHEAD-CASING FATIGUE ANALYSIS","authors":"Fabiano Guimarães","doi":"10.1115/1.4063011","DOIUrl":"https://doi.org/10.1115/1.4063011","url":null,"abstract":"\u0000 This paper presents a fully coupled solution in the time-domain, using the finite-differences method to the system of equations that model the dynamic behavior of the riser, blow out preventer and casing strings, when connected for well drilling/completion – the model is suitable to evaluate wellhead fatigue, even when the amplitude of oscillation and accelerations of the BOP are high. Sensibility analysis is used to show the effect of changing the Riser Top Tension to the resulting maximum values of wellhead bending moment and casing stress ranges. For the case where the rig is oscillating around a fixed position and there is no current, using a regular wave, the results show that there are some wave periods for which an increase in the Riser Top Tension reduces the maximum wellhead bending moment and the max casing stress range, therefore increasing fatigue life of the casing and wellhead. The effects of varying the weight of the BOP and soil parameters and the effect of the phase difference between the wave and first order vessel motion are analyzed. The proposed solution can also be used to perform riser and casing analysis during drift-off/drive-off.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46908491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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